Minimum delay between consecutive transmit

I have a dedicated task that processes a fifo which queues incoming USB requests.
This task loops into that fifo and processes requests then builds the replies and transmit them by calling 'USB_WriteEPTimed' function passing the replies buffers.

Everytime this dedicated task is waked up by a signal, it processes all the fifo before sleeping and waiting for next signal.

The call to 'USB_WriteEPTimed' is very close one to the other, so what should be the delay between each call to that function ?

Currently, no wait is used and some 256 bytes long payloads are not transmitted because '_WaitForEndOfTransfer', from 'USB_WriteEPTimed', exits with 'timeout' status.